Magnetic transducer



Dec. 16, 1969' 1.. E. KRONFELD MAGNETIC TRANSDUCER Filed Oct. 10, 1967 I INVENTOR. LEON/W0 E KPQNFELQ ATTOPNEKS United States Patent G M 3,484,564 MAGNETIC TRANSDUCER Leonard E. Kronfeld, Minneapolis, Minn., assignor to The Nortronics Company, Inc., Minneapolis, Minn., a corporation of Minnesota Filed Oct. 10, 1967, Ser. No. 674,190 Int. Cl. Gllb 5/00; G01d 15/12 U.S. Cl. 179100.2 6 Claims ABSTRACT OF THE DISCLOSURE A core holder for use in a magnetic transducer including a housing member and an insert fixedly positioned therein for receiving at least a portion of the core and maintaining said core fixedly positioned relative to the housing member. The insert is constructed with a portion thereof operating in a spring-like fashion to automatically position the core, along at least one major axis of the core with respect to the housing member.

BACKGROUND OF THE INVENTION Field of the invention This invention pertains to a new and improved magnetic transducer and more particularly to an improved core holder for use in magnetic transducer constructions.

In the magnetic transducer industry, devices referred to as core holders are utilized to maintain the magnetic cores of the transducers in a desired position during assembly, which core holders are normally integrated into the finished transducer. The core holders are constructed in a variety of forms. In general, they are hollow, somewhat rectangularly shaped structures adapted to mate with other core holders to form an enclosure. The side of a core holder which adjoins a mating core holder is open to form a core and winding receiving cavity within the enclosure.

Each of the core holders contains at least one generally U-shaped core piece. The core pieces are fixedly positioned in the associated core holder so that the tips, which are the extreme fiat surfaces at the ends of the core pieces that cooperate with a second core piece to form front and rear magnetic flux gaps, extend outwardly into the open side of the core holder. The core tips are lapped, generally utilizing certain pads or portions of the open side of the core holder as a reference, to place the tips as closely in a plane as possible. In some instances the manufacturer attemps to place the core tips and the pads in a common plane and in some instances the core tips are in a plane spaced from a plane through the pads; however, this is not critical to the present invention and will not be elaborated upon further.

The assembled core holder and associated core pieces make up a body section that is usually described as a half section. Prior to assembly of the body sections, electrical windings are positioned around portions of the cores. When the body sections are joined to form a transducer, the enclosure formed by the core holders is generally open at the rear and receives a termial board therein having the electrical connection for the windings thereon. A flux gap is formed between the front core tips of mating core pieces in a transducer, the dimensions of which are critical to the magnetic characteristics thereof. The relative positions of the rear core tips are generally important also; however, the magnetic flux gap between the front core tips is the gap usually utilized for tape contact and, therefore, to simplify this disclosure the front core tips will be referred to simply as core tips with the understanding that the rear core tips are included where appropriate.

3,484,564 Patented Dec. 16, 1969 Description of the prior art In the prior art, core holders are generally formed by casting, molding, or machining a nonmagnetic material into the desired shape. The core holder has a cavity therein with a slot-like depression formed in the inner surface of the lower wall and a mating slot formed in the front wall. The depression in the lower wall and the mating slot in the front wall generally form a continuous groove adapted to receive a core piece therein. The cavity in the core holder is large enough so that an electrical winding can be positioned over the core piece therein. In this prior art a completely new core holder must be designed each time a variation, such as additional tracks, etc. is incorporated into the transducer. Thus, separate dies, molds, or the like must be utilized to produce each variation of transducer.

SUMMARY OF THE INVENTION In the present transducer a core holder is utilized which includes a housing member and an insert fitted therein. The housing member, which may be a standard housing member that is utilized in a large series or variety of core holders, may be produced in a variety of ways, such as extruding, stamping, etc.; and because it has very little or no details formed on the inner surface of the walls, it may be produced in a manner which is simpler and less expensive than molding or casting. In the embodiment which will be described in the following specification, the housing is stamped and formed from a flat piece of material into the desired shape; however, it should be understood that a variety of other methods might be utilized to produce the housing which would still be within the scope of this invention. In general the housing is constructed of a non-magnetic material which has the proper workability so that the housing member can easily be formed therefrom, but which has suflicient hardness and strength so that later operations, such as grinding and lapping, can be performed.

An insert, which is constructed from a non-magnetic material, such as plastic or the like, having a desired amount of resiliency is designed to fit within the housing and provide all of the inner details for the core holder. The insert in the first embodiment to be described, is produced from a flat piece of material which is stamped and formed into the desired shape. Core piece receiving channels are formed within the core holder by the insert; and a portion of the insert in juxtaposition to each channel provides spring bias on the core piece inserted therein. The spring bias on the core piece tends to correctly position and maintain the core piece within the channel. .To produce variations in core holders a variety of inserts are produced which contain the desired variations in detail, such as different numbers of core piece receiving channels.

With respect to any particular transducer, openings or slots are formed in the front wall of the housing member to correspond to the number of channels desired. An insert, chosen from a variety of available inserts, having the desired number of core piece receiving channels is fixedly positioned within the housing member. The housing member and the various inserts each have means as sociated therewith which cooperate to correctly position the insert within the housing member. The portion of the insert acting as a spring correctly positions the core piece within the core holder in a transverse direction and the assembler positions the core piece along the channel in the insert to correctly position the core piece axially.

Thus, in the present device a standard housing member is utilized with any one of a variety of inserts to produce a great variety of core holders. Because a standard housing member is utilized to receive the insert, the cost of the core holder is greatly reduced. Also, because methods such as stamping or the like may be utilized to produce the housing members and the inserts, the cost of production of the core holders is greatly reduced while the speed or amount of production is greatly increased. Also, because spring means are incorporated within the insert to correctly position and hold the core pieces therein, assembly time of the transducers is greatly reduced.

It is an object of this invention to provide a new and improved transducer. It, is a further object of this invention to provide a standard housing member which is adapted to receive any of a variety of inserts therein to produce a great variety of core holders.

It is a further object of this invention to provide a core holder which is relatively inexpensive and simple to produce.

It is a further object of this invention to provide an insert and a housing member which cooperate to produce a core holder that aids in correctly positioning and that will hold the core pieces placed therein.

These and other objects of this invention will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings, wherein like characters indicate like parts throughout the figures:

FIGURE 1 is a view in perspective of a housing member;

FIGURE 2 is a view in perspective of an insert;

FIGURE 3 is a view in top plan of the insert illustrated in FIGURE 2;

FIGURE 4 is a view in top plan of the core holder, including the insert illustrated in FIGURE 2 positioned in the housing illustrated in FIGURE 1, illustrating core pieces inserted therin;

FIGURE 5 is a view in side elevation of the core holder illustrated in FIGURE 4, parts thereof broken away and shown in section;

FIGURE 6 is a view in side elevation of a somewhat different embodiment of a core holder;

FIGURE 7 is a detailed view of a corner of the embodiment of the core holder illustrated in FIGURE 6;

FIGURE 8 is a view in perspective of another embodiment of an insert; and

FIGURE 9 is a diminutive view in perspective of an assembled pair of core holders.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGURE 1 illustrates a housing member generally designated 10 having side walls 11 and 12, a front wall 13 and'a lower wall 14. The housing member 10 is adapted to mate with another housing member 10 to form a generally box-shaped enclosure as shown in FIGURE 9.

The side wall 11 has a front and a rear portion 18 and 19 and the side wall 12 has a front and a rear portion 20 and 21 respectively. The rear portions 19 and 21 are laterally offset from the front portions 18 and 20 to form a discontinuity or steps 22 and 23 in each of the side walls 11 and 12. As specifically shown, each step extends the entire width of its associated side wall and is located at approximately'the longitudinal center thereof. It should be understood, however, that a discontinuity in the side walls 11 and 12 could be embodied in many forms'other than by steps 22 and 23 as specifically shown; and it is intended that the term discontinuity, as used herein, includes all forms of structure which would perform the functions to be explained presently.

In the present and preferred embodiment of the invention, the housing member 10, is made from a flat blank of nonmagnetic metallic material, such as brass, and stamped and formed for a dual-track transducer. A pair of core piece receiving openings 25 and 26 are formed in the front wall 13. The openings 25 and 26 are substantially rectangular in shape and in the present embodiment are formed by shearing the material from the upper edge of the front surface 13 downwardly and forcing the material outwardly to form outwardly extending lips 27 and 28, respectively. It should be understood that the material in the openings 25 and 26 could be removed completely, but the lips 27 and 28 are formed in the present embodiment for the purposes which will be explained presently. A-pair of inwardly extending disk-shaped extrusions 29 and 30 are formed on the inner surface of the lower wall 14- in a spaced apart relationship adjacent the rear edge of the lower wall 14. An axially extending slot 31 is formed in the lower wall 14 and is adapted to receive a magnetic shield therein. Adjacent the rear end of each of the side walls 11 and 12 is a rectangularly shaped notch 32.and 33, respectively. The notches 32 and 33 when joined with similar notches in the opposite mating housing form rectangularly shaped openings adapted to receive the ends of a terminal board, not shown, therein. The terminal board contains the electrical connections of the winding in the finished transducer.

Although a dual-track or binaural transducers are illustrated in the drawings, it should be understood that the housing member 10 can be adapted for use in dilferent types of transducers. If a monaural or single-track transducer is desired, a single core piece receiving opening is formed in the front wall 13. Also, if more than two tracks are desired more than two core pieces receiving openings are formed in the front wall 13. In each embodiment, the position-of the opening in the front wall 13 must conform to the desired position of the front edges of the core tips in the core holders. The position of the openings in the front wall 13 of the housing member 10 will be described in more detail presently.

FIGURES 2 and 3 illustrate one form of insert generally designated 35 which is adapted to fit within the housing 10. The insert 35 is generally rectangular in shape and may be stamped or otherwise formed of material having the desired resiliency. While it should be understood that insert 35 can be made from any material, preferably non magnetic, having the desired resiliency and thickness, such as plastic, metal, etc., in the present embodiment, insert 35 is made relatively thin and, therefore, is constructed from a beryllium copper alloy. Also, a number of variations may be incorporated in the insert 35. to produce different types of transducers, uch as monaural, binaural, etc. The proper type of insert 35 is incorporated in a housing member 10 having the desired number of openings in the front wall thereof to produce monaural, binaural, etc., core holders. For example, in the present embodiment, housing 10 is formed for a binaural head, thus insert 35 is shown to be for a binaural or two-track head.

The front edge of the insert 35 is designated 36, the rear edge is designated 37, One side is designated 38 and the other side is designated 39. The sides 38 and 39 of the insert 35 are separated into front portions 40 and 42 and rear portions 41 and 43. The rear portions 41 and 43 are laterally outwardly offset at 44 and 45 from the front portions 40 and 42. The otfsetdistance is not critical but should be sufficient to allow the front edgesof the rear portions 41 and 43 of the insert 35 to butt against the rear edges of the front portions 18 and 20 of the housing member 10 when the insert is correctly positioned therein; The offsets at 44 and 45 in the insert 35 are positioned rearwardly from the front edge 36 a distance such that when positioning the insert 35 front to back within. the housing member 10, the front edges of the rear portions 41 and 43 of the insert 35 will abut the rear edges of the front portions 18 and 200i the housing member 10, indicated as steps 22 and 23, respectively, without front edge 36 engaging front wall13. v I 1 The insert- 35 is retained in the correct position within the housing member 10 during assembly of the core holder by the following means. The distance between the outer surfaces of the rear portions 41 and 43 of the insert 35 is slightly greater than the distance between the inner surfaces of the rear portions 19 and 21 of the housing member 10. When insert 35 is positioned within the housing member the rear portions 41 and 43 of the insert 35 are forced inwardly by the rear portions 19 and 21 of the housing member 10. Since the entire insert 35 is constructed of a resilient material the rear portions 41 and 43 thereof produce substantially equal forces outwardly on the rear portions 19 and 21 of the housing member 10. Thus, the rear portions 41 and 43 of the insert 35 act as springs to position the insert 35 correctly within the housing member 10 from side-to-side or in a lateral or transverse direction.

The insert 35 has a pair of circular openings 46 and 47 which are positioned adjacent the rear edge 37 thereof and have a diameter somewhat larger than the extruded portions 29 and 30 of the housing member 10. When the insert 35 is placed in the housing member 10 so that the front edges of the rear portions 41 and 43 of the insert 35 are abutting the rear edges of the front portions 18 and 20 of the housing member 10, the openings 46 and 47 are generally coaxial with the extruded portions 29 and 30 of the housing member 10. The offsets at 44 and 45 in the insert 35 and the discontinuities 22 and 23 in the housing member 10, are utilized to correctly position the insert 35 front to back within the housing member 10, and the spring-like rear portions 41 and 43 of the sides 38 and 39 correctly position the insert 35 transversely within the housing member 10. When the insert 35 is correctly positioned within the housing member 10 the extruded portions 29 and 30 extend slightly above the insert 35 through the openings 46 and 47. The insert 35 is fixedly engaged within the housing member 10 by riveting the part of the extruded portions 29 and 30 extending through the openings 46 and 47 in the insert 35.

The insert 35 has a pair of slots 50 and 51 formed therein which extend from the front edge 36 rearwardly and angle obliquely toward the sides 38 and 39, respectively. Front and rear upstanding flanges 52 and 53 are spaced apart along the inner edge of slot 50' and are formed by turning a portion of the material from the slot 50 upwardly. In a similar fashion, front and rear upstanding flanges 54 and 55 are formed and spaced apart along the inner edge of slot 51. A single upstanding flange is formed, in a manner similar to the flanges 52-55, at the outer edge of each of the slots 50 and 51; and these two flanges are designated 56 and 57 respectively. The flanges 56 and 57 each have integral therewith an additional portion of material designated 58 and 59, respectively, which portions extend forwardly and slightly inwardly to partially overlie the slots 50 and 51. More particularly, portion 58 is integral with flange 56 and overlies a portion of slot 50; and portion 59 is integral with flange 57 and overlies a portion of slot 51. The additional portions of material 58 and 59 provide a force inwardly generally perpendicular to the axial length of the slots 50 and 51 when said portions are flexed outwardly; and they will be referred to as spring means 58 and 59 in the remainder of this specification. The slots 50 and 51 in the insert 35 cooperate with the housing member 10 to form core piece receiving channels. It should be understood that the core piece receiving channels can be formed in a variety of ways and shapes; and the term channel is used broadly in this specification to mean that area defined by the insert or by the insert and housing which is adapted to receive a core piece therein.

In FIGURE 3, the position of a core piece 60 is illustrated in dotted lines in the slot 51 to show the approximate relationship of the various flanges 54, 55 and 57. The distance between the two flanges 54 and 55 on one side of the slot 51 and the single flange 57 on the opposite side of the slot 51 is slightly greater than the width of the core piece 60. The distance between the two flanges 54 and 55 on one side and the forwardmost core engaging portion of the spring means 59 on the opposite side is somewhat less than the width of the core piece 60 so that the spring means 59 must be flexed outwardly to place the core piece 60 in the slot 51; and spring means 59 urges the core piece 60 into the correct transverse position in the slot 51.

A centrally located slot 65 having a pair of upstanding flanges 66 on one side thereof and a single upstanding flange 67 on the opposite side extends axially between the slots 50 and 51. The two flanges 66 and the opposite flange 67 are formed by turning a portion of the material from the slot 65 upwardly. The slot 65 is aligned with the slot 31 in the housing member 10 when the insert 35 is correctly positioned therein and is adapted to receive a piece of magnetic shielding material therein to prevent cross-talk or magnetic interaction be tween the two tracks.

When the insert 35 is correctly positioned within the housing member 10 and fixedly engaged therein, the entire assembly constitutes a core holder generally des ignated 70 in FIGURES 4 and 5. Core holder 70 is illustrated in FIGURES 4 and 5 with the core piece 60 in the slot 51, and a second core piece 71 engaged in the slot 50. When the core pieces are fixed in position in the core holder, it makes a transducer body section described as a half-section. When the core piece 60 is correctly p0sitioned in the slot 51, the spring means 59 urges the core piece 60 into abutment with the rearmost flange 55 and an edge of the opening 26. In a similar fashion the spring means 58 urges the core piece 71 into abutment with the rearmost flange 53 and an edge 74 of the opening 25. Neither of the core pieces 71 or 60 rest against the forwardmost flanges 52 and 54 of the insert 35 since the inner edges 74 and 75 of the openings 25 and 26 are utilized as reference edges in the correct positioning of the core pieces.

To insure that the rearmost flanges 53 and 55 and the edges 74 and 75 will always operate to position the core pieces 71 and 60, front flange 52 is slightly removed or laterally offset from the plane defined by the side of flange 53 which engages core piece 71 and edge 74 and, similarly, front flange 54 is laterally offset from the plane defined by flange 55 and front edge 75. This offset must be at least equal to the maximum allowable transverse variation or tolerance in the position of the core pieces 60 and 71, also bearing in mind the tolerances in the front slots 25 and 26, so that in the worst allowable cases the adjacent surface of the core pieces 71 or 60 would just contact its associated front flange 52 or 54, respectively. In spite of this offset, front flanges 52 and 54 function to aid in the positioning of said core pieces 71 and 60.

An upstanding flange 76 and 77 is illustrated at the rearmost ends of the slots 50 and 51. These flanges 76 and 77 are utilized in the further assembly of the transducer and do not form a part of the present invention. In general, the core pieces 71 and 60 will not contact the flanges 76 and 77, however, in some special cases they may.

The core pieces 71 and 60 are correctly positioned in the slots 50 and 51 in a transverse direction by the action of the spring means 58 and 59 of the insert 35. The core pieces 71 and 60 are then positioned, front to back, until the front edges of the tips thereof extend through the openings 25 and 26 in the front wall 13 of the housing member 10 the proper distance. This proper positioning may be accomplished either manually or automatically through the use of proper fixtures-and the like; and as means for accomplishing this are well known in the magnetic art, it need not be discussed further.

A plane extending through steps 22 and 23 is a reference plane for the front to back adjustment of the core pieces. This plane is shown by dotted lines in FIG. 4, and is indicated by the numeral 81. Core pieces 71 and 60 are positioned downwardly to butt against a reference portion of housing member 10 to provide the up and down position of the front tips of core pieces 71 and 60. This reference can be either the top surfaces of lips 27 and 28 or the inside surface of wall 14. In constructions which do not utilize lips 25 and 26, the inner horizontal edge of housing 10 defining the depth of openings 25 and 26 might be used as a reference. It might also be mentioned that the inside surface of front wall 13 has been used in the pastas a reference for the front to back adjustment; and if desired to do so, it may still be utilized in the present invention by moving the core pieces forwardly until they butt against such surface. It might be mentioned in connection with the preferred embodiments of the invention shown that it is a distinct advantage to utilize steps 22 and 23 on the reference plane for the front to back adjustment as previously described and withsuch steps 22 and 23 also functioning as reference surfaces for the spring clips as described in copending application.(see page 16).

Thus, the form of core holder 70 as shown brings together in a desirable and improved cooperative relationship the development of the spring clips as described in said copending application, Ser. No. 580,981, and its development of the preferred form of the instant invention.

The necessary accurate positioning of core pieces is known in the magnetic art and various reference surfaces and edges have been used. Without going into this in any further detail, three significant aspects of the invention in this respect might be mentioned at this point. First, the invention provides for the lateral or side to side adjustment of the core piece; second, spring means 58 and 59 hold the core piece in position to be further adjusted, front to back, etc.; and then, they maintain the proper position of the core pieces until the core pieces are suitably bonded or afiixed to the core hold. Also, the invention provides for an available reference plane in steps 22 and 23 for the front to back adjustment of the core pieces.

After the core pieces 60 and 71 are positioned in the core holder 70, they are fixedly engaged therein by suitable means such as applying epoxy or other suitable adhesive material thereto. The front tips 72 and 73 and the back tips of the core pieces 71 and 60 are then lapped to form a smooth uniform plane surface, which when joined with the tips of core pieces in a mating core holder with a suitable gap spacer, between the front tips of mating half sections, of foil or otherwise, will form a uniform accurate flux gap. In general, the upper surfaces'lS, 16, and 17 of the side walls 11 and 12 and the front wall 13, respectively, are utilized as reference surfaces during the lapping to insure that the front tips 72 and 73 and the back tips of the core pieces lie in a desired plane, which will be parallel with the plane containing the tips of the core pieces in the mating core holder. The lapping pro duces a pressure on the front wall 13 which might tend to move or bend the front wall 13 relative to the remainder of the core holder. To prevent such movement of the front wall 13, each of the corners between the side walls 11 and 12, and the front wall 13, are reinforced at 78 and 79. In this embodiment the reinforcement at 78' and 79 is a continuous portion integral with the side walls 11 and 12, and the front wall 13, which portion is formed into corners during the stamping and bending of the housing member 10.

' With the core pieces 71 and 60 fixedly engaged in the core holder 70, and the tips 72 and 73 properly lapped, a mating c'ore holder is joined therewith to form a generally box-like hollow structure or enclosure 80, illustrated in FIGURE 9. The illustration of the box-like structure 80 in FIGURE 9 does not illustrate a method of attaching the two core holders 70 together, since there are several means for this purpose. Preferably, however, the two core holders are attached by the spring clips described in the previously mentioned copending application entitled, Improved Magnetic Transducer, Ser. No. 580,-

981, filed'Sept. 21, 1966 and which need not be further described herewith. While the structure might be utilized as a transducer in the form illustrated in FIG- URE 9, once assembled it generally is placed within a case, not shown, having a similar shape but somewhat larger dimensions. The case is constructed of a material which shields the transducer from stray magnetic flux as well as other harmful effects. The case has a pair of openings in the front thereof to receive the front edge of the tips 72 and 73 of the core pieces 71 and 60 therethrough. In the assembly of the structure 80 within the case, it is important that the core pieces 60 and 71 do not touch the sides of the case.

As shown in FIG. 4, portions of lips 27 and 28, indicated by the numerals 82 and 83, extend laterally outwardly beyond the the adjacent edges of the core pieces 71 and 60. Edges 82 and 83 can be used as reference edges abutting the adjacent sides of the case openings, not shown, to maintain a controlled spacing between the core pieces and a case later assembled around the housing.

A different embodiment of the reinforced corners of the housing member 10 is illustrated in FIGURES 6 and 7, wherein components similar to those in the first embodiment are designated with similar numerals having a prime added. In this embodiment, the front wall 13 and the side walls 11' and 12' are stamped from a flat piece of material and are an integral part of the lower wall 14'. The front wall 13 has a pair of tabs and 91 extending outwardly from either end thereof. To form the housing member 10 the side walls 11' and 12 are bent upwardly at an angle of approximately 90 with the lower wall 14', and the front wall 13' bent upwardly at an angle less than 90. The tabs 90 and 91 are bent rearwardly at an angle of approximately 90 to the front wall 13' in juxtaposition with portions of the side walls 11' and 12' respectively. The tabs 90 and 91 are fixedly attached to the side walls 11 and 12 by some means such as brazing, welding, riveting, etc., and reinforce the front wall 13' so that it does not move during subsequent assembl operations, such as lapping and polishing of the core tips and/or the upper surface 17' thereof.

FRIGURE 8 shows a different embodiment of the insert for'use in housing 10. This insert of FIGURE 8 is designated generally by the numeral 35'; and its components similar to insert 35 are designated with similar numerals having a prime added. Insert 35 is non magnetic and is formed of a molded plastic. Rear lateral edges 41' and 43' extend laterally outwardly beyond front lateral edges 40' and 42' to provide shoulders or abutment portions 44' and 45. Shoulders 44' and 45 abut the rear edges of the front portions 18 and 20 of housing member 10, which rear edges are the steps 22 and 23, to position the insert in housing 10 in a front to back relationship. Edges 41' and 43 in juxtaposition wtih rear portions 19 and 20 position insert 35 in the proper side-to-side relationship with housing member 10. Insert 35' is fixed to housing member 10 by a suitable adhesive; Slots 50' and 51 form core piece receiving channels. Resilient arms 58 and 59' form spring means, each along one side of a different one of the channels 50 and 51. The opposite channel forming walls are designated by the numerals 92 and 93 respectively; and each wall is divided into a front portion and a rear portion. The rear portion of wall 92 is designated by the numeral 53' and the front portion of the numeral 52'. The rear portion of wall 93 is designated by the numeral 55 and the front portion by the numeral 54. A core piece or, if laminated, core pieces, received into channel 50' will flex the resilient arm 58' laterally outwardly; and arm 58 will engage and bias the said core piece toward and into engagement wtih rear wall portion 53'. Similarly, a core piece received into channel 51 will engage and'bias the said core piece toward and into engagement with rear Wall portion 55. In a core holder assembly, shown in FIG. 4 with respect to insert 35, front wall portions 52 and 54' preferably will not engage but will be closely adjacent the core pieces received into their respective channels 50' and 51 and, wherein the core pieces will be biased one against edge 74 and rear wall portion 53 and the other against edge 75 and rear wall portion 55'.

In view of the more complete explanation of insert 35 and the similarity between insert 35 and 35', further description of insert 35' is believed to be obvious. It might be mentioned, however, that insert 35' is formed with a shield receiving slot 94.

Thus, an improved magnetic transducer comprised of mating core holders, each including a housing member and an insert, has been disclosed. The housing member can be made in a standard form, and a variety of single and multi-track transducers can be produced by utilizing inserts which vary slightly from the one disclosed. Because of this adaptability and because of the simplicity of the housing members and the inserts, the manufacturing cost per unit is minimized. Also, the insert holds and positions the core pieces within the core holder, thus reducing assembly time and the number of operations.

While I have shown and described specific embodiments of this invention, I desire it to be understood, therefore, that this invention is intended to be defined and covered solely by the appended claims.

What is claimed is:

1. A magnetic transducer comprising:

(a) a housing member,

(b) non-magnetic insert means fixedly positioned in said member;

(c) said housing member having a pair of laterally spaced abutment portions;

(d) said insert means having a pair of laterally spaced abutment portions engaging said first mentioned abutment portions for positioning said insert member in said housing;

(c) said insert means and said housing member cooperating to form a core holder having at least one channel therein with a portion of said insert means forming spring means adjacent said channel,

(f) magnetic core means positioned in said channel and maintained in a desired position by said spring means,

(g) a portion of an edge of said channel defined by said insert cooperating with a portion of the housing member to form a first reference plane for positioning said magnetic core means in said housing,

(h) said spring means being positioned opposite said first reference plane to urge said core means against said portions defining said first reference plane; and

(i) said first mentioned abutment portions being disposed in a plane transverse to said first reference plane and adapted to be used as a second reference plane in the positioning of said core means in said housing.

2. A magnetic transducer as set forth in claim 1 comprising a pair of like housing members, each having a front wall, two side walls, a bottom wall and an open top, the open tops of each housing member being positioned in juxtaposition to provide a box-like enclosure; and said insert means comprising an insert member fixedly positioned in each housing member; said two side walls of each housing member having a discontinuity which defines said first mentioned abutment portions; and the front wall of each housing member having at least one slot formed therein for receiving a portion of the magnetic core means therethrough.

3. A magnetic transducer as set forth in claim 2 Wherein each of the housing members is formed from a stamped metal blank and the corners between the front and side walls are formed to reinforce said front wall.

4. A magnetic transducer comprising:

(a) a housing member having a front wall, two side walls, a bottom wall and an open top;

(b) non-magnetic insert means of dissimilar material than said housing member and fixedly positioned in said housing member adjacent said bottom wall;

() said side walls being formed to define a pair of laterally spaced co-planar abutment portions adjacent said bottom wall;

(d) said insert means having a pair of laterally spaced abutment portions engaging said first mentioned abutment portions for positioning said insert member in said housing;

(e) said insert means and said housing member co operating to form a core holder having at least one channel therein with a portion of said insert means forming spring means adjacent said channel;

(f) magnetic core means positioned in said channel and maintained in a desired position by said spring means;

(g) said front wall having at least one slot formed therein for receiving a portion of the magnetic core means therethrough;

(h) a portion of said insert means defining said channel and a portion of said housing member defining said slot cooperating to form a first reference plane for positioning said magnetic core means in said core holder;

(i) said spring means being positioned opposite said first reference plane to urge said core means against said portions defining said first reference plane; and

(j) the plane of said first mentioned abutment portions defining a second reference plane for positioning said magnetic core means in said core holder.

5. A core holder for a magnetic transducer comprising:

(a) a housing member having a front wall, two side walls, a bottom wall and an open top, and adapted to be joined with at least one other housing member to form a generally box-like enclosure;

(b) a core piece supporting insert fixedly attached to the housing member;

(c) said front wall of the housing member having at least one slot formed therein, and one edge of said slot and a portion of said insert being positioned in relation to each other to serve as a reference plane for the positioning of a core piece in a core holder; and

(d) inwardly extending discontinuities formed in said two side walls for use in correctly positioning the core piece supporting insert therein, said discontinuities being coplanar and defining a second reference plane for the positioning of a core piece in the core holder.

6. A core holder as set forth in claim 5 having in addition at least two protrusions on the inner surface of the lower wall for receiving the insert thereover and holding said insert fixedly in place.

References Cited UNITED STATES PATENTS 3,340,518 9/1967 Hanson 179-1002 3,357,097 12/1967 Schulte 179100.2

STANLEY M. URYNOWICZ, 112., Primary Examiner JEROME P. MULLINS, Assistant Examiner US. Cl. X.R. 340-1741; 34674 

